Effect of temperature on ergosterol biosynthesis in yeast.

Anaerobically grown Saccharomyces cerevisiae was aerated for 7 hr at 20 degrees, 30 degrees, or 40 degrees, in a phosphate buffer containing 2% glucose. At elevated temperature (40 degrees), de novo synthesis of squalene and sterois in the aerated yeast was only 32-35% of that at lower temperature (20 degrees or 30 degrees), and this decrease was attributed to the repression of the enzymes involved in the synthesis of mevalonate from acetyl-COA. In addition, at elevated temperature, the metabolic flux from squalene to ergosterol was blocked at squalene epoxidation, lanosterol demethylation, and ergosta-5, 7, 22, 24(28)-tetraene-3beta-ol reduction.